Helmut sell



A ril 124.1927.

H. SELL 'MICROPI-IONIC RELAY Filed May 6. 1925 Patentedv Apr. 12, 1927.

UNITED STATES PATENT-OFFICE.Q

niinuu'r SELL, or imnnmsmmnnssrap'r, GERMANY, ASSIGNOB TO sin-mans a I HALsxE, Ax'rmNeEsnLLscnArn'or SIEMENSSTADT, GERMANY, a conrona'rron or 021mm.

MICROPHONIC 1 RELAY.

Application filed Kay 6, 1925, Serial No. 28,447,:1nd in Gerinany September 18, 1924.

The present invention'relates to improvements 1n 'microphon1'c relay-s in which the input currents energize an electro-magnetic system by means of which amicrophone diaphragm is oscillated. By the formerly known amplifying relays of this kind the transmitted oscillations especially those of voice frequency are more or less distorted.

The object of the inventionis to avoid this drawback by transmitting the received current in a moreexactmanner. than formerly known. a The invention is especially suited for devices for which the vacuum tube amplifiers-whichi recently have -replaced the microphone amplifiers for most' pur-' posesare not suited. This is for instance the case in hearing apparatuses for thedeaf, where the entire outfit is carried by the person using it and which must therefore be of a simple construction as the individuals using the same are unskilled persons; Also for radio apparatuses it is important that the elements are-simple and easily operated,

} so that the microphone is especially suited for sealso in radio outfits.

In the formerly known microphone amplifiers the distortion of the voice oscillations are partly due to the microphone contact and partly to the oscillating element acting. upon the contact, which element, while in most cases of diaphragm shape was heretofore designed on incorrect principles.

v According to the invention an essential improvement in the known arrangements is obtained .by using as a microphone diaphragm a metal foil which is Iradially.

stretched and which is oscillated by means .of a magnet system which acts upon a circular armature plate centrally-fastened to the foil. Further characteristic features will appear from the specification.

In the drawing some constructional forms of the invention are shown by way of examples.

Fig. 1 is a section through an amplifier microphone according to the invention.

Fig. 2 is a detail.

Fig. 3 shows a further constructional form of the amplifier according to the invention.

Fig. 4 shows in perspective view a magparts of the amplifier according to Fig. 5.

In a casingl madeof vulcanized rubber or any other insulating material a magnet system is located, the pot-shaped radially slotted or divided soft iron core 2 of which has a central pole 3 adjacent to which the edge 4 of the outer pole'is situated in such I a position that only-a narrow annular air gap separates thesame. My means of a cover 5; the magnet system is kept in its place n the casing or box-1. The casing 1 also contains a diaphragm 6 of ahigh 'grade' elastical materiahl preferably. I phosphorbronze the thickness of which is only a few hundred parts of a millimetre or thinner. The edges of this foil are soldered to a sup-l porting ring 7 which rests against an abut ment'S in the casing. To the central part of the foil a disc shaped iron armature is soldered which has a thickness of only some tenth part of a millimetre anda diameter of a. few millimetres, so. that it just covers the air gap of the exciter magnet system aforementioned. On account of the small mass of the oscillatingsystem good damping may be obtained. By means 0 forcible str'etch- I ing to be described present y combined-with small dimensions the natural frequency of.

the system may be kept. outside the range of the normal voice frequencies. Practical y its natural frequency ranges aboveone thousand oscillations per second- It is'important to note that the system practically possesses one natural frequency only because the central part only performs reciprocating oscillationsand 'no formation. of nodes will take place on account of the small mass of" the foil ed 'e z0ne. A.

The forcible stretching of the-diaphragm is obtained by pressing the edge ll'ofthe' microphone cell 10 against the diaphragm (3 adjacent to the supporting ring 7. The pressure is effected bymeans of a cover 12 which is screwed into the casin The central part of the microphone cell It) contains a space for the resistance material 13 which is surrounded by a felt ring of contact points.

The very'considerable resistance between the diaphragm and the material which otherwise naturally would arise is prevented. because the element in contact with the material consists of metal and not of carbon. To further improve the contact the diaphragm is provided with a coating of gold or platinum, whereby the side facing the granulated carbon always remains clean and a formation of oXides,'which alters the resistance, is prevented.

The side of the microphone cell lying remote from the diaphragm comprises a carbon plate or a metal plate 15 of a precious metal or a plate provided with a precious metal coatin In spite of the fact that the contacts between metal and carbon usually are regarded as being poor, the effect of the present microphone arrangement is extremely satisfactory, because the resistance at the contact point of the two materials is small and the change of resistance takes place over a proportionately long way between a greatnumber of succeeding small particles. whereby the amplitude of the diaphragm is small in comparison to the length of the path in the granulated carbon.

I11 order to prevent disturbing elastic reactions from the felt ring 14 this ring is madeof such dimensions that it is maintained under pressure when it is located in place. It is also possible to dowithout the ring 14 in which case the microphone cell. 10 is almost filled with granulated carbon as shown in Fig. 2. To prevent a short-circuiting of the effective central parts of the carbon tilling through the outer parts of the same which are subjected only to small alterations in pressure and resistance. the conducting counter plate 15 is cent ally arranged. so that the outer parts of the carbon filling will not come into action. The same etlect may be obtained by applying to the edge of the diaphragm and ofthe counter plate a coating of varnish.

It is further possible to improve the effects of the amplifier by arranging the carbon cellbetween two diaphragms each of which is operatedeby a magnet system 2 2 respectively. as shown in Fig. The stretching of the diaphragm is effected in this case in the following manner. In the casing 1 the diaphragm 6 is first located, its supporting ring 7 resting on a shoulder providcd'in the casing. On the diaphragm 6 rests a ring 16 which forms the carbon cell and against the other side of which the second diaphragm (3" is placed. .The supporting ring 7 of the latter diaphragm is supported by a casing part 17 which is screwed into the casing 1 and in which the second magnet 2 is fastened by means of a cover 5. \Vhen screwing the part l'l'into its place the diaphragms 6 and 6 are stretched.

As shownin Fig. 4 instead of a potshaped soft iron magnet a permanent magnet 18 may be used, the one pole piece 1!) of which surrounds the other pole piece 20 in such a manner that also here an annular gap of relatively small diameter faces the armature. 18 denotes the exciting coils for the microphone.

The Figs. 5. 6 and 7 show a further embodiment of the invention, which on account of its small dimensions and its other advantageous properties is very Well suited for use for instance for aural telephone devices for persons hard of hearin According to this constructional form the apparatus consists of a casing 21 of hard rubber and a metallic cover 22 connected to it by a thread 23 inwhich cover a magnet system and a microphone controlled by the former are located. This magnet system may have a soft iron core or a permanent magnet core. The system shown is of the latter type. It consists of a ring of steel 24 magnetized in diametral direction as indicated by the letters N and S in Fig. 7 To the south-pole S is rigidly connected a sector-shaped piece 25 of iron at the end of which an iron core 26 isv arranged coaxially with the ring 24. To the lower part S of the ring magnet 24 adisc 28 of soft iron is fixed-by a spacing piece 27 of nonmagnetic material which disc is fixed to the upper part N of the ring by an iron piece 2!). The (bed 28 is provided with a projecting part 30 and with a radial slot 31 preventing the flow of short-circuit currents. In the plane of the projecting part 30 this disk forms the north pole and the end of the core 26 forms the south-pole of the magnetic system. On the pin 26 is arranged the winding 31 controlling the microphone. The magnet system is inserted into the casing 21 and a bushing 32. adapted to load the winding terminals 33 out of the casing, is guided in a slot 34 of the casing 2l.

lla') On the rim of the disc 28 a distance ring 35 of nonmagnetic metal is laid and upon this ring the microphone 15 arranged. The

,microphone comprises a diaphragm 35 Jill diaphragm is kept permanentlyspanned eor stretched by n'ieans ot' a bgdHS 'con taining the microphone cell an 01 g providcd with an annular edge 39 which is pressed against the foil 35 by means of the inwardly turned edge of casing 40 which clamps together the slmporting ring 36 and the edge of the microphone cell 38. In the microphone cell a filling 41 preferably of granulated carbon is used as resistance matc-rial and the peripheral parts of the diaphragm are preferably damped by means of a felt ring 42, so that only the central part of the diaphragm. which has the greatest amplitude. comes into action.

I In the bottom of the microphone cell 38 an opening is formed into which a cylindrical projection 43 of a metal plate 44 projects in such a manner that it presses with its inner face against the carbon filling 41. This plate and also the entire microphone cell are held in place. by the cover 22 ot the casing fll. The projection 43 as well as the walls and sides of the microphone cell may partly or completely be coveredwith a coatin" of gold or platinum.

The electrical connection of the projection '43 is formed by a metal cap 45 put over the cover 22 at the edge ofwhich a bifurcated tongue 46 is arranged. This tongue straddles a bolt 47 on casing 21. One ot' the plugs 48 is connectedto the bolt 47 and the other plug 4-8. is connected to diaphragn'rSS (connection not shown). This may illustrate how the microphonic relay may be connected for instance to a dry battery.

What I claim as my invention and desire to secure b Letters Patent is:

1. In. a microphonic relay a radially stretched metal foil diaphragm. a disc'shaped iron armature centrally located upon the foil. an operating magnet comprising an outer annular ,pole'and aninner pole stud. the inner pole being spaced from the outer pole so that only a narrow annular air gap'separates the poles. said armature being of sutficicntsize to bridge said annular gap.

2. In an'iicrophonic relay a metal toil dia phragm. an iron armature centrally located upon the diaphragm. a pot-shaped exciting magnetcomprising an outer annular pole and an inner pin shapcd pole, the inner pole being spaced from the outer pole by a narrow intermediate air gap said armature be- .centrically, located in relation to the ing of suflieient size to bridge said gap, and a casing surrounding the entiredevice.

3. In a microphonic relay a metal foil diaphragm, an iron armature centrally located upon the diaphragm, a pot-shaped exciting magnet comprising an outer annular polo having a radial slot. and an inner pin-shaped pole. the inner pole being spaced from the outer pole by a narrow iutcrmcdiate'air gap said armature being of sutiicient size to bridge said gap. and a casing surrounding the entire device. v

4. In a microphonic relay :1 phragm. a supporting ring to which .the said foil is fastened. an iron armature centrally located upon the same, pole pieces acting upon the. armature. a microphone cell closed by said diaphragm, a casing surrounding the entire device andbeing consaid microphone cell and the said diaphragm, an annular shoulder in the casing adapted to hold the said supporting ring and the said diaphragn'i in fixed relation to the other elements' of the amplifier when the said diametal foil an phragm and the said supporting ring are pressed against the said seat by means of the microphone cell.

5. In a microphonic relay a metal foil diaphragm. a supporting ring to which the said foil is fastened. an iron armature centrally located upon the same. pole pieces acting upon the armature. a circular microphone cell having an annular rim, said diaphragm having a coating of a precious metal and closing said cell across said annular rim. and a filling of finely granulated carbon enclosed in said cell. a casing surrounding the entire device and being concentrically located in relation to the said. microphone cell and the said diaphragm, an annular shoulder inthe casing adapted to hold the said supporting ring and the said diaphragm in fixed relation to the other elcmentsof the amplifier when the said diaphragm and the said supporting ring are pressed against the said seat by means of the microphone cell. and means tor pressing said cell against said diaphragm. I

(i. In a microphouic relay a metal foil dia phragm, a supporting ring to Wl'llClltllG said toil is fastened. an iron armature centrally located upon the same. pole pieces acting upon the arn'iature. a circular microphone cell having an annular rim. said diaphragm haviiig a coating of a precious metal and closing said cell across said rim and a filling ot' finely granulated -arbon enclosed in the said cell. means for preventing the peripheral parts of the microphone diaphragm in partaking in the oscillations. :ncasing surrounding the entire device and being concentrically located in relation to the said microphone cell and the said diaphragm, an anloo ill

nular shoulder in said casing adapted to hold the said supporting ring and the said diaphragm in fixed relation to the other elements of the relay when the said diaphragm and the said supporting ring are pressed against the said shoulder by means of the microphone cell, and means for pressing said cell against the diaphragm.

' 7. In a microphonic relay a metal foil diaphragm. a supporting ringto which the said foil is fastened, an iron armature centrally located upon thesame, pole pieces acting upon .the armature, a circular microphone cell having an annular rim. said diaphragm having a' coating of a precious metal and closing said cell across said rim and a filling of finely granulated carbon enclosed in the said cell, a casing surrounding the entire device and being concentrically located in relation to the said microphone cell and the said diaphragm, an annular shoulder in said 'casing adapted to hold thesaid supporting ring and the said diaphragm'in fixed relation to the other elements of the relay, when the said diaphragm and the said supporting ring are pressed against the said seat by means of the microphone cell, and covers at both ends of the said casing for holding the different members of the relay to ether.

8. In a microphonic relay a diaphragm, an iron armature centrally fixed on said diaphragm, a casing forming with said diaphragm a microphone cell, a filling of contact material in said cell, a ring-shaped per:

manent magnet diametrically magnetized, an iron pin arranged in central axial relation to said magnet, an element magnetically connecting said pin to one of the poles of said magnet, an exciting Winding surrounding said pin, an annular pole'piece surrounding the free end of said pin in spaced relation to the same, and another element magneticall connecting said pole piece to the other p0 e of said magnet, said armature being suitably Spaced from the pin and said circular pole .ieee to bridge the gap between said twoelements.

9. In a microphonic relay a metal foil diaphragm, a supporting ring to which the said l'oil is fastened,'an iron armature. centrally located upon the same, a ring-shaped diametrically magnetized magnet, a sectorshaped element rigidly fastened to one pole of said ring-shaped magnet and radially arranged in relation to the same, an iron pin disposed in axial alinement with said magnet andbeing fastened to the inner end of the said sector-shaped element, an exciting coil' for the microphone surroundin the said iron pin, aradially slotted soft iron disc arranged in spaced relation to the said ringshaped magnet and to the said. metal foil diaphragm, coaxially with and in parallel to these elements. two distance pieces connecting the said soft iron disc to the said magnet,

one distance piece being of' non-magnetic material and being arranged adjacentto one pole of the magnet, the other distance piece being of a magnetic material and being arranged adjaccnt to the other pole of the magnet. a central annular projection on the said soft iron disc. surrounding the free end of the said iron pin to'form a gap, a washer separating the said soft iron disc from the said diaphragm supporting ring, a circular body having a central aperture. and an ammlar flange adapted to be pressed against the said diaphragm adjacent to its periphery for stretching the diaphragm,- a clamping ring surrounding the peripheries of the diaphragm supporting ring and the said circular body, a metal plate having a central cap which projects through the central aperture in the said circular body and together with the annular flange of the same and the dia phragm serves to form a microphone cell, a peripheral felt ring and a carbon filling in the said cell and means for holding the several parts of the device together.

10. In a .microphonic relay a metal foil diaphragm, a supporting ring to which the said foil is fastened. an iron armature cent ally located upon the same, a ring-shaped diametrically magnetized magnet, a sectorshaped element rigidly fastened to one pole of said ring-shaped magnet and radially arranged in relation to the same, an iron pin disposed in axial alinement with said magnet and fastened to the inner end of the said sector-shaped element, an exciting coil for the microphone surrounding the said iron pin, a radially slotted soft iron'disc arranged in spaced relation to the said ringshaped magnet and to the said metal foil diaphragm coaxially with and in parallel to these elements, two distance pieces connecting the said soft iron disc to the said magnet," one distance piece being of nonmagnetic material and being arranged adjacent to one pole of the magnet, the other distance piece being of a magnetic material and being arranged adjacent to the other loo Ill)

pole of the magnet, a central annular projection on the said soft iron disc, surrounding the free end of the said iron pin to form a gap, a washer separating the said soft iron disc from the said diaphragm supporting ring, acircular body having a central apertur'e and an annular flange adapted to he pressed against the said diaphragm adjacent to its periphery for stretching the (ha-- phragm, a clamping ring surrounding the peripheries of the diaphragm supporting ring and the said circular body, a metal plate; having a central cap which projects through the central aperture in the said circular body and togcthcravith the annular flange of the same and the diaphragm serves to form a microphone cell. a peripheral feltring and a filling of granulated carbon in the said cell. a mating of precious metal 0n ing the said holiling' ring to the said conthe diaphragm portions and the cap c0m taint-ielenwnt and means for connecting the ing into mntavt with the carbon filling a said outer ring to the said containing 010- 10 container element encompassing the said difment. I

fen-nt parts, a threaded holding ring serv- In testimony whereof I afiix my signature. iug to retain the several difi'erent parts in the container element, altouter ring for fix- HELMUT SELL. 

